Process for the production of methylenedicarbanilates

ABSTRACT

A process is described for producing methylenedicarbanilates by reacting carbanilates with formaldehyde in the presence of a specific catalyst. The catalyst is selected from (1) a cation exchanger containing sulfonic acid groups which has a proton exchange capacity of at least 0.1 meq/g, (2) a clay having an acidity of at least 0.1 meq/g at an acidic site, the acid strength of the acidic site being -3.0 or less as a value of acidity function H o , (3) a mixed oxide having an acidity of at least 0.1 meq/g at an acidic site, the acid strength of the acidic site being -3.0 or less as a value of acidity function H o , (4) heteropolymolybdic acid, and (5) heteropolytungstic acid.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Ser. No. 192,979, filed Oct. 1, 1980.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for the production of methylenedicarbanilates. More particularly, this invention provides a process for the production of methylenedicarbanilates; i.e., an intermediate product for use in the production of 4,4'-diphenylmethanediisocyanate which is generally called "MDI" and an important starting material for the production of polyurethanes.

2. Description of the Prior Art

MDI is used as a starting material for the production of polyurethane elastomers, elastic fibers, adhesives, coating resins, etc., and recently its production has been sharply increasing. At present, MDI is produced by a method which comprises reacting aniline with formaldehyde to give 4,4'-diaminodiphenylmethane and reacting the 4,4'-diaminodiphenylmethane with phosgene. This method, however, has the disadvantages in that the use of harmful phosgene is necessary, the phosgenation step is complicated, and that hydrochloric acid by-produced in the phosgenation step must be disposed of safely.

In addition to the phosgenation process, various methods have been proposed for the production of isocyanates, including: (1) a method in which aromatic carbamates are produced by reacting aromatic nitro compounds with carbon monoxide and alcohol in the presence of a catalyst comprising palladium, Lewis acid, e.g., iron chloride, and a heterocyclic base, e.g., pyridine [see Japanese Patent Application (OPI) No. 98240/1976 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application")] and then decomposed by heating; (2) a method in which the same reaction is carried out in the presence of a catalyst comprising palladium, vanadyl chloride and a heterocyclic base [see Japanese Patent Application (OPI) No. 22339/1979], and a method in which the same reaction is carried out in the presence of a catalyst comprising selenium, sulfur and a base [see Japanese Patent Application (OPI) No. 62420/1974].

SUMMARY OF THE INVENTION

As a result of extensive investigations to produce methylenedicarbanilates by employing as a starting material the carbanilates which are advantageously obtained by the above described methods, it has now been found that methylenedicarbanilates can commercially advantageously be produced by reacting carbanilates with at least one selected from the group consisting of formaldehyde, oligomers of formaldehyde, acetals of formaldehyde, acylals of formaldehyde and oxymethylenebiscarboxylates in the presence of at least one acid catalyst selected from the group consisting of: (1) a cation exchanger containing sulfonic groups which has a proton exchange capacity of at least 0.1 meq/g, (2) a clay having an acidity of at least 0.1 meq/g at an acidic site, the acid strength of the acidic site being -3.0 or less as a value of acidity function H_(o), (3) a mixed oxide having an acidity of at least 0.1 meq/g at an acidic site, the acid strength of the acidic site being -3.0 or less as a value of the acidity function H_(o), (4) heteropolymolybdic acid and (5) heteropolytungstic acid.

This invention, therefore, provides a process for producing methylenedicarbanilates which comprises reacting carbanilates with at least one selected from the group consisting of formaldehyde, oligomers of formaldehyde, acetals of formaldehyde, acylals of formaldehyde and oxymethylenebiscarboxylates in the presence of at least one acid catalyst selected from the group consisting of: (1) a cation exchanger containing sulfonic groups which has a proton exchange capacity of at least 0.1 meq/g, (2) a clay having an acidity of at least 0.1 meq/g at an acidic site, the acid strength of the acidic site being -3.0 or less as a value of acidity function H_(o), (3) a mixed oxide having an acidity of at least 0.1 meq/g at an acidic site, the acid strength of the acidic site being -3.0 or less as a value of acidity function H_(o), (4) heteropolymolybdic acid and (5) heteropolytungstic acid.

DETAILED DESCRIPTION OF THE INVENTION

Carbanilates used as a starting material in this invention can be represented by the general formula: ##STR1## wherein R is an alkyl group containing from 1 to 4 carbon atoms or a phenyl group, and X, Y and Z are each hydrogen, a halogen atom, a nitro group, an alkyl group containing from 1 to 5 carbon atoms, an alkoxy group containing from 1 to 5 carbon atoms, or an alkoxycarbamoylphenylmethyl group wherein the alkoxy portion contains 1 to 4 carbon atoms. In particular, methylcarbanilate, ethylcarbanilate, phenylcarbanilate, 2,4'-methylenebis(ethylcarbanilate), 4,4'-methylenebis(ethylcarbanilate), etc. are preferably used. These carbanilates can be used alone or in combination with each other.

The formaldehyde may be used in various forms, such as a gaseous form or as an aqueous solution. While the formaldehyde can be used as an aqueous solution, it is preferred to reduce the amount of water in the starting material since the condensation reaction of this invention is a dehydration reaction and the reaction rate is larger as the concentration of water in the reaction system is smaller. Additionally, oligomers of formaldehyde, e.g, trioxane, paraformaldehyde, etc., acetals of formaldehyde, e.g., methylal, etc., acylals of formaldehyde, i.e., reaction products of formaldehyde and aliphatic carboxylic acids, e.g., methylidene diacetate, and oxymethylenebiscarboxylates can be used. Hereinafter, the above-mentioned compounds (including formaldehyde) are referred to as "formaldehyde compounds".

While the ratio of formaldehyde compounds to carbanilate is not critical, when the reaction rate, selectivity of the desired product, amounts of high boiling point by-products being formed, etc. are taken into account, it is generally preferred that the carbanilate is used in an amount of at least 2 moles per mole of formaldehyde compounds (converted to a formaldehyde basis), with the range of from about 3 to 10 moles being particularly preferred.

Although the process of this invention can be carried out without solvents, it is desirable to use solvents which are inert to the reaction, in order for the reaction to smoothly proceed. Solvents which can be suitably used in this invention include alkanes such as pentane, hexane, octane, etc., cycloalkanes such as coclohexane, etc., aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, etc., ethers such as tetrahydrofuran, dioxane, diphenyl ether, etc., ketones such as acetone, ethyl methyl ketone, cyclohexanone, etc., alkanols such as methanol, ethanol, butanol, octanol, etc., aliphatic carboxylic acids such as acetic acid, propionic acid, etc., aliphatic carboxylic acid esters such as ethyl acetate, etc., nitroalkanes such as nitromethane, etc., aromatic nitro compounds such as nitrobenzene, nitrotoluene, dinitrotoluene, etc., halogenated alkanes such as dichloromethane, dichloroethane, trichloroethane, etc., aromatic halogenated compounds such as chlorobenzene, dichlorobenzene, etc., nitriles such as acetonitrile, benzonitrile, tolunitrile, etc., amides such as N,N-dimethylformamide, N,N-dimethylacetoamide, etc., sulfoxides such as dimethylsulfoxide, etc., and cyclic sulfones such as tetrahydrothiophen-1,1-dioxide, etc.

Representative examples of cation exchangers containing sulfonic acid groups which have a proton exchange capacity of at least 0.1 meq/g include a styrene-divinylbenzene copolymer, a phenol-formaldehyde copolymer, a perfluoroethylene polymer into which a sulfonic acid functional group or groups are introduced, sulfonated coal, a sulfonated polyphenyl, a sulfonated polyphenylene oxide, a sulfonated cellulose, ect. Of these cation exchangers containing sulfonic acid groups, examples of such cation exchangers available on the market are listed in Table 1.

                  TABLE 1                                                          ______________________________________                                         Cation Exchangers                                                              Containing                                                                     Sulfonic Acid                                                                  Groups       Trade Name   Manufacturer                                         ______________________________________                                         Sulfonated styrene-                                                                         Diaion SK 106                                                                               Mitsubishi                                           divinylbenzene            Chemical                                             copolymer                 Industry Ltd.                                                     Diaion HPK 25                                                                               Mitsubishi                                                                     Chemical                                                                       Industry Ltd.                                                     Amberlite 200                                                                               Rohm & Haas Co.                                                   Amberlyst 15 Rohm & Haas Co.                                                   Dowex 70     Dow Chemical Co.                                     Sulfonated perflu-                                                                          Nafion 501   Dupont Co.                                           oroethylene                                                                    polymer                                                                        Sulfonated phenol-                                                                          Duolite C-10 Diamond Shamrock                                     formaldehyde              Corp.                                                polymer                                                                        Sulfonated coal                                                                             Permutit H-53                                                                               Permutit A.G.                                        Sulfonated   Celex SE     Biolad Co.                                           cellulose                                                                      ______________________________________                                    

Almost all of the above cation exchangers containing sulfonic acid groups which are available on the market have a proton exchange capacity of from 1 to 10 meq/g. Since the use of those cation exchangers having small proton exchange capacities generally lowers the reaction rate, it is desirable to use cation exchangers having sulfonic acid groups which have as high a proton exchange capacity as possible.

As a typical cation exchanger containing sulfonic acid groups, a styrene-divinylbenzene copolymer with sulfonic acid functional groups introduced therein is known. A styrene-divinylbenzene copolymer crosslinked with from 2 to 18% by weight of divinylbenzene is generally available on the market. Particularly preferred are those which are generally referred to high porous or macroreticular type cation exchangers containing sulfonic acid groups, e.g., Diaion HPK 25, Amberlite 200, Amberlyst 15, Dowex 70, etc., as illustrated in Table 1. These cation exchangers give good results.

A clay or mixed oxide having an acidity of at least 0.1 meq/g at an acidic site, the acid strength of the acidic site being -3.0 or less as a value of acidity function H_(o), can also be used as a catalyst of this invention. The value of acidity function of H_(o) =-3.0 corresponds approximately to an acidity of 48% by weight sulfuric acid.

As such a clay, natural or synthetic clays such as kaolinite, attapulgite, chlorite, Fuller's earth, bentonite, montmorillonite, halloysite, smectite, illite, vermiculite, sepiolite, mordenite, zeolite, etc. can be used. These clays have a cation exchange capability, and in order to further increase this activity, they are preferably subjected to protonation by treatment with an inorganic acid, e.g., hydrofluoric acid, hydrochloric acid, perchloric acid, sulfuric acid, etc., or by thermally decomposing an ammonium salt of the clay.

Examples of mixed oxides which can be used in this invention are shown in Table 2 together with their H_(o) values.

                  TABLE 2                                                          ______________________________________                                         Mixed Oxide    H.sub.o Value                                                   ______________________________________                                         ZrO.sub.2 --CdO                                                                               ca. -3.0                                                        SiO.sub.2 --ZnO                                                                               "                                                               TiO.sub.2 --CdO                                                                               "                                                               TiO.sub.2 --ZnO                                                                               "                                                               TiO.sub.2 --SnO                                                                               "                                                               SiO.sub.2 --La.sub.2 O.sub.3                                                                  ca. -4.0                                                        ZrO.sub.2 --Al.sub.2 O.sub.3                                                                  ca. -5.7                                                        TiO.sub.2 --Al.sub.2 O.sub.3                                                                  ca. -5.7                                                        SiO.sub.2 --Y.sub.2 O.sub.3                                                                   "                                                               SiO.sub.2 --Ga.sub.2 O.sub.3                                                                  ca. -7.0                                                        TiO.sub.2 --ZrO.sub.2                                                                         ca. -8.2                                                        SiO.sub.2 --Al.sub.2 O.sub.3                                                                  "                                                               SiO.sub.2 --ZrO.sub.2                                                                         "                                                               SiO.sub.2 --TiO.sub.2                                                                         "                                                               ______________________________________                                    

Heteropolymolybdic acid or heteropolytungstic acid are formed by the polycondensation of molybdic acid anion (MoO₄ ²⁻) or tungstic acid anion (WO₄ ²⁻) with oxyacid anion, e.g., phosphoric acid anion (PO₄ ³⁻), silicic acid anion (SiO₄ ²⁻), chromic acid anion (CrO₄ ²⁻), etc. As the central element, there can be mentioned, in addition to phosphorus, silicon and chromium, titanium, zirconium, vanadium, manganese, iron, cobalt, nickel, rhodium, platinum, copper, aluminum, gallium, germanium, tin, arsenic, selenium, tellurium, iodine, cerium, thorium and the like.

Examples of heteropolymolybdic acids are H₃ Mo₁₂ PO₄₀, H₄ Mo₁₂ TiO₄₀, H₈ Mo₁₂ CeO₄₂, H₈ Mo₁₁ GeO₃₉, H₆ Mo₉ MnO₃₂, H₅ Mo₆ IO₂₄, H₉ MO₆ CrO₂₄, H₆ Mo₁₈ As₂ O₆₂, etc. Examples of heteropolytungstic acids are H₃ W₁₂ PO₄₀, H₄ W₁₂ SiO₄₀, H₃ W₁₂ VO₄₀, H₆ W₆ TeO₂₄, H₆ W₁₈ P₂ O₆₂, etc. Heteropolyacids obtained by replacing part of the condensed coordinating element, i.e., molybdenum and tungsten, with such an element as vanadium, such as H₅ Mo₁₀ V₂ PO₄₀, H₆ W₉ V₃ PO₄₀, etc., can be used in this invention. In addition, acidic salts obtained by replacing part of the proton of heteropolyacids with a metal ion, such as HCs₃ Mo₁₂ SiO₄₀, HCuW₁₂ PO₄₀, etc., can be used in this invention.

The process of this invention can be carried out at a temperature of from 0° C. to 250° C., and preferably carried out at from about 20° C. to 150° C. The catalyst is suspended in a liquid phase or the liquid phase is passed through a fixed bed of the catalyst. When heteropolymolybdic acid, heteropolytungstic acid, or its acidic salt is used, the reaction can be carried out in a uniform liquid phase because they are strong acids and soluble in water or various organic solvents. If desired, the heteropolyacid is deposited on a suitable carrier, and the reaction can be carried out using a suspended bed or a fixed bed catalyst arrangement.

The amount of the catalyst used is not critical. When the reaction is carried out by suspending the catalyst in a liquid phase or carried out in a uniform liquid phase, it is used in an amount of from 0.1 to 500 mmoles, preferably from 1 to 100 mmoles, per mole of carbanilate, or 10 to 1,000 meq per mole of carbanilate. In the case of carrying out the reaction in a fixed bed catalyst, the flow rate of the starting material carbanilates is from about 0.1 to 100 moles/hr per liter of the catalyst.

When ethylcarbanilate, for example, is used as a starting material in the practice of this invention, the main products obtained are: 4,4'-methylenebis(ethylcarbanilate), represented by the formula (I): ##STR2## 2,4'-methylenebis(ethylcarbanilate), represented by the formula (II): ##STR3## and dimers represented by the formulae (III), (IV) and (V): ##STR4##

The dimers represented by the formulae (III), (IV) and (V) are all isomerized in the presence of an acid catalyst and converted into methylenebis(ethylcarbanilate) represented by the formulae (I) and (II). Therefore, by returning the dimers represented by the formulae (III), (IV) and (V) to the reaction system, the yield of methylenebis(ethylcarbanilate) can be further increased.

The following examples are given to illustrate this invention in greater detail.

EXAMPLE 1

A 100 ml glass reactor equipped with a stirrer and a reflux condenser was charged with 46.5 mmoles of ethylcarbanilate, 3.33 mmoles of trioxane, 30 ml of benzene and 5 ml of a cation exchanger containing sulfonic acid groups (Amberlyst 15, produced by Rohm & Haas Co.) and they were reacted with stirring for 270 minutes while refluxing at 84° C.

Gas chromatographic and high speed liquid chromatographic analyses of the reaction solution showed that the conversion of ethylcarbanilate was 32.3%, the amount of 2,4'-methylenebis(ethylcarbanilate) (hereinafter referred to as "2,4'-MDU") formed was 0.93 mmoles, and the amount of 4,4'-methylenebis(ethylcarbanilate) (hereinafter referred to as "4,4'-MDU") formed was 7.75 mmoles.

EXAMPLES 2 AND 6

The same reactor as used in Example 1 was charged with catalyst, starting materials, and solvent in the amounts as shown in Table 3, and they were reacted in an analogous manner as in Example 1 under the conditions as shown in Table 3. In the same manner as in Example 1, the reaction solution was analyzed. The results are shown in Table 4.

EXAMPLES 3 TO 5

A 100 ml glass reactor equipped with a stirrer and a circulating azeotropic dehydrating apparatus was charged with the catalyst, starting materials and solvent in the amounts as shown in Table 3, and they were reacted while dehydrating continuously under azeotropic conditions. In the same manner as in Example 1, the reaction solution was analyzed. The results are shown in Table 4.

EXAMPLES 7 TO 10, 12 TO 20

In the same reactor as used in Example 1 or Examples 3 to 5, the catalyst, starting materials and solvent in the amounts as shown in Table 3 were reacted under reflux conditions or while continuously dehydrating under azeotropic dehydrating conditions. These reaction conditions are shown in Table 3. The reaction solution was analyzed in the same manner as in Example 1. The results are shown in Table 4.

EXAMPLE 11

Through a glass reaction tube with an inner diameter of 10 mm which had been charged with 10 ml of Diaion HPK-25 and placed in an oil bath at 80° C., ethylcarbanilate, trioxane and benzene were passed at flow rates of 21.3 mmoles/hr, 1.41 mmoles/hr and 15 ml/hr, respectively. After 165 minutes from the start of the reaction, an effluent was taken out and analyzed. The conversion of ethylcarbanilate was 25.0%, and the yields of 2,4'-MDU and 4,4'-MDU were respectively 0.48 mmoles/hr and 4.42 mmoles/hr.

                                      TABLE 3                                      __________________________________________________________________________     Catalyst          Starting Materials    Solvent    Reaction                                                                              Reaction             Ex-          Amount     Amount     Amount     Amount                                                                              Temperature                                                                           Time                 ample                                                                              Type     (ml) HCHO  (mmoles)                                                                            Carbanilate                                                                          (mmoles)                                                                            Type  (ml) ( C.)  (hrs)                __________________________________________________________________________     2   Amberlite 200.sup.(3)                                                                   5    Trioxane                                                                             3.33 EPU.sup.(1)                                                                          46.8 Benzene                                                                              30   *84      4.5                3   Nafion 501.sup.(4)                                                                      2.4 g                                                                               "     6.66 "     50   Benzene                                                                              10   **101  6                                                            Toluene                                                                              20                               4   Diaion HPK-25.sup.(5)                                                                   5    "     3.33 "     "    Benzene                                                                              30   **85   2                    5   "        "    "     6.66 MPU.sup.(2)                                                                          100  Cyclo-                                                                               60   **     "                                                            hexane                                 6   "        2.5  37%   0.81 g                                                                              EPU   50   Dioxane                                                                              30   *85    6                                      Formalin                                                     7   "        5    Trioxane                                                                             33.3 "     100  Benzene                                                                              60   *77    3                    8   "        2.5  "     1.67 "     50   "     30   **85   6                    9   "        1.3  "     3.33 "     "    "     "    **86   1                    10  "        10   "     8.3  "     "    "     "    **83   5                    12  HPA.sup.(6)                                                                             0.5  "     6.66 "     "    Benzene                                                                              10   **101  1/4                               mmoles                                                                              "                     Toluene                                                                              20                               13  "        0.2  "     1.65 "     22.5 Benzene                                                                              15   31       7.5                             mmoles                                                            14  HPA.sup.(7)                                                                             1.0 g                                                                               "     3.33 "     47.5 "     30   83       5.5                15  KSF/O.sup.(8)                                                                           2.0 g                                                                               "     "    "     46.8 "     "    *      2                    16  KSF/O.sup.(8)                                                                           2.0 g                                                                               Trioxane                                                                             8.52 EPU   51.1 Benzene                                                                              30   *      1                    17  "        "    "     5.83 "     47.2 "     "    *      4                    18  "        "    37%   0.81 g                                                                              "     48.4 Dioxane                                                                              "    *      "                                      Formalin                                                     19  Zeolon 100.sup.(9)                                                                      "    Trioxane                                                                             3.33 "     48.0 Benzene                                                                              "    *      "                    20  Silica.sup.(10)                                                                         5    "     "    "     50.0 Toluene                                                                              "    *110   6                        Titania                                                                    __________________________________________________________________________      Note:                                                                          .sup.(1) Ethylcarbanilate                                                      .sup.(2) Methylcarbanilate                                                     .sup.(3) Cation exchanger containing sulfonic acid groups, produced by         Rohm & Haas Co.                                                                .sup.(4) Sulfonated perfluoroethylene resin, produced by Dupont Co.            .sup.(5) Cation exchanger containing sulfonic acid groups, produced by         Mitsubishi Chemical Industries, Ltd.                                           .sup.(6) Phosphomolybdic acid (H.sub.3 Mo.sub.12 PO.sub.40)                    .sup.(7) Silicotungstic acid (H.sub.4 W.sub.12 SiO.sub.40)                     .sup.(8) Montmorillonite KSF/O, produced by Gardler Chemical Co.               .sup.(9) Synthetic zeolite, produced by Norton Co.                             .sup.(10) Si/Ti = 1/6.93                                                       *Under reflux conditions                                                       **Under azotropic conditions                                             

                  TABLE 4                                                          ______________________________________                                                Conversion of.sup.(1)                                                                      Yield.sup.(2)                                                      Carbanilate (mmoles)                                                    Example  (%)           2,4'-MDU  4,4'-MDU                                      ______________________________________                                         2        29.5          0.81      7.49                                          3        60.6          0.84      11.4                                          4        32.0          0.85      10.2                                          5        24.5          0.14.sup.(3)                                                                             8.48.sup.(4)                                  6        15.2          0.15      3.00                                          7        64.3                                                                  8        16.3                                                                  9        16.4                                                                  10       56.0                                                                  12       34.5          1.03      12.69                                         13       26.5          0.19      2.73                                          14       6.9           0.06      0.54                                          15       34.4          0.40      14.2                                          16       51.0          0.23      3.74                                          17       57.6          0.81      13.8                                          18       9.3           0.03      0.35                                          19       1.2           0.05      0.18                                          20       5.0                     0.44                                          ______________________________________                                          Note:                                                                          ##STR5##                                                                       (the conversion of carbanilate in Examples 1, 11 and 21 was obtained in        this manner)                                                                   .sup.(2) The yield was calculated based on the results of high speed           liquid chromatographic analysis using:                                         apparatus: duPont's 830 type                                                   column: Zonbax Sil, 4.6 φ × 250 mm                                   carrier: Chloroform, 0.8 ml/min, 700 psig                                      internal standard: diethyl phthalate                                           detector: UV 254 mm                                                            In the analysis, the peak size of each component against the peak of           internal standard on the chromatogram was indicated as an area ratio, and      the absolute amount of each component was calculated according to the          following expression, for which the calibration factor was previously          calculated with respect to the internal standard.                              Amount (produced) of component A =                                             ##STR6##                                                                                                                                                      used amount of internal standard × calibration factor                    (The yield of the reaction product in Examples 1, 11 and 21 were obtained      by the abovementioned manner.)                                                 .sup.(3) 2,4'-methylenebis (methylcarbanilate)                                 .sup.(4) 4,4'-methylenebis (methylcarbanilate)                           

EXAMPLE 21

Through a glass reaction tube with an inner diameter of 10 mm which had been charged with 10 ml of Montomorillonite KSF/O (produced by Gardler Chemical Co.) and placed in an oil bath at 86° C. was passed at a flow rate of 2.5 ml per hour a solution prepared by mixing in a ratio of 51 mmoles of ethylcarbanilate, 3.33 mmoles of trioxane and 30 ml of toluene. After 210 minutes from the start of the reaction, an effluent was taken out and analyzed. The conversion of ethylcarbanilate was 35.5%, and 2,4'-MDU and 4,4'-MDU were produced in 0.033 mmoles/hr and 0.732 mmoles/hr, respectively.

EXAMPLES 22 TO 35

In a 200 ml three necked flask equipped with a thermometer, refluxcondenser and a stirrer, ethylcarbanilate, trioxane (or a 35% aqueous solution of formaldehyde) and a solvent were placed, in the amounts shown in Table 5, and additionally 5 ml of the catalyst as shown in Table 5 was added thereto. They were reacted at 80° C. for a predetermined period of time (see Table 5) in an oil bath.

By analyzing the solution formed by high speed liquid chromatography, the conversion of ethylcarbanilate, and the yields of methylenebis(ethylcarbanilate) (hereinafter referred to as "MDU"), and 4,4'-MDU were determined. The results are shown in Table 6.

                                      TABLE 5                                      __________________________________________________________________________                               Solvent      Reaction                                              EPC.sup.(1)                                                                         HCHO.sup.(2)   Amount                                                                              Time                                    Example                                                                             Catalyst (mmoles)                                                                            (mmoles)                                                                              Type    (ml) (hrs)                                   __________________________________________________________________________     22   Diaion HPK 25                                                                           50.12                                                                               10.02.sup.(3)                                                                         Acetic Acid                                                                            30   4                                       23   Diaion HPK 40                                                                           50.32                                                                               10.06.sup.(3)                                                                          "      "    2                                       24     "      50.12                                                                               10.02.sup.(3)                                                                         Toluene 60   2                                       25     "      50.28                                                                               10.06.sup.(3)                                                                         Chlorobenzene                                                                          30   4                                       26   Diaion HPK 55                                                                           50.45                                                                               10.09.sup.(3)                                                                         Acetic Acid                                                                            "    4                                       27     "      50.03                                                                               10.01.sup.(3)                                                                         Chlorobenzene                                                                          "    4                                       28     "      50.45                                                                               10.09.sup.(3)                                                                         Toluene 60   3                                       29   Montmorillonite                                                                         50.03                                                                               10.01.sup.(3)                                                                         Acetic Acid                                                                            30   8                                            KSF/O                                                                     30   Montmorillonite                                                                         50.02                                                                               10.00.sup.(3)                                                                          "      "    4                                            KSF/O                                                                     31   Montmorillonite                                                                         50.03                                                                               10.01.sup.(3)                                                                         Acetic Acid                                                                            30   8                                            KSF/O                Chlorobenzene                                        32   Montmorillonite                                                                         50.15                                                                               10.03.sup.(3)                                                                         Toluene 60   2                                            KSF/O                                                                     33   Diaion HPK 40                                                                           51.61                                                                               10.32.sup.(4)                                                                         Acetic Acid                                                                            30   4                                       34   Diaion HPK 55                                                                           50.78                                                                               10.15.sup.(4)                                                                         Toluene "    9                                       35   Montmorillonite                                                                         48.40                                                                               10.00.sup.(3)                                                                         Dioxane "    4                                            KSF/O                                                                     __________________________________________________________________________      Notes:                                                                         .sup.(1) Ethylcarbanilate                                                      .sup.(2) Trioxane and a 35% by weight aqueous solution of formaldehyde         were converted to and are indicated on a formaldehyde basis.                   .sup.(3) As trioxane.                                                          .sup.(4) As a 35% by weight aqueous solution of formaldehyde.            

                  TABLE 6                                                          ______________________________________                                         Conversion of.sup.(1)                                                                          Yield.sup.(2)                                                  EPC             (%)                                                            Example (%)         Dimer.sup.(3)                                                                            MDU    4,4'-MDU                                  ______________________________________                                         22      80.8        --        56.1   52.2                                      23      100.5       60.8      49.4   46.5                                      24      67.7        48.1      39.0   35.7                                      25      83.8        53.0      50.3   46.3                                      26      94.7        --        64.6   61.0                                      27      96.1        --        48.0   44.7                                      28      76.8        52.8      47.3   44.0                                      29      89.8        87.3      44.0   41.5                                      30      81.4        84.6      22.1   20.8                                      31      82.0        77.8      31.1   29.7                                      32      40.1        28.8      22.5   21.9                                      33      84.7        84.2      43.1   40.6                                      34      61.6        56.2      37.0   34.8                                      35      22.5         8.3       3.8    3.5                                      ______________________________________                                          Note:                                                                          .sup.(1) Conversion of ethylcarbanilate (based on formaldehyde)                ##STR7##                                                                       .sup.(2) Yield (based on formaldehyde)                                         The yield was calculated based on the results of the high speed liquid         chromatographic analysis using:                                                apparatus: Hitachi pump control unit 635 Type and Shimadzu SPD1 type           detector                                                                       column: Zonbax Sil 4.6φ × 250 mm                                     carrier: nhexane/chloroform (40/60 vol. %) 1.5 ml/min., 1035 psig               internal standard: 4,4'-methylenebis(methylcarbanilate)                       detector: UV 254 mm                                                            In the analysis, the peak size of each component against the peak of           internal standard on the chromatogram was indicated as an area ratio, and      the absolute amount of each component was calculated according to the          following expression, for which the calibration factor was previously          calculated with respect to the internal standard.                              amount (produced) of component A =                                             ##STR8##                                                                                                                                                      used amount of internal standard × calibration factor                    yield of MDU (%) =                                                             ##STR9##                                                                                                                                                      yield of 4,4'-MDU (%) =                                                        ##STR10##                                                                                                                                                     .sup.(3) Accumulated yield of compounds represented by the formulae (I),       (II), (III), (IV) and (V).                                               

EXAMPLES 36 TO 44

In a 200 ml three necked flask equipped with a thermometer, reflux condenser, and a stirrer, ethylcarbanilate, formaldehyde compound, 30 ml of a solvent and a catalyst were placed, and then reacted at a predetermined temperature on an oil bath for a predetermined period of time. By analyzing the solution formed by high speed liquid chromatography, the conversion of ethylcarbanilate, and the yields of dimer, MDU and 4,4'-MDU were determined.

The amounts of ethylcarbanilate and formaldehyde used, the type of the solvent, the reaction temperature, the type and amount of the catalyst, and the reaction time are shown in Table 7. The results are shown in Table 8.

                  TABLE 8                                                          ______________________________________                                         Conversion of.sup.(1)                                                                          Yield.sup.(2)                                                  EPC             (%)                                                            Example (%)         Dimer.sup.(3)                                                                            MDU    4,4'-MDU                                  ______________________________________                                         36      99.5        68.1      68.1   64.4                                      37      89.1        58.4      58.4   55.4                                      38      88.4        56.2      20.9   20.3                                      39      89.0        72.0      55.8   53.1                                      40      91.5        60.4      60.4   57.5                                      41      61.6        60.0       1.9    1.9                                      42      85.6        66.1      66.1   62.7                                      43      16.4        --        --     --                                        44      66.3        41.5      19.2   18.1                                      ______________________________________                                          Note:                                                                          .sup.(1), .sup.(2), .sup.(3) Same as defined in Table 6.                 

EXAMPLES 45 TO 65

In the same reactor as used in Examples 22 to 35 ethylcarbanilate, formaldehyde compound, a catalyst and a solvent were placed in predetermined amounts, and were reacted at 80° C. on an oil bath for a predetermined time, as shown in Table 9. By analyzing the solution formed by high speed liquid chromatography, the conversion of ethylcarbanilate and the yields of dimer, the MDU and 4,4'-MDU were determined. The results are shown in Table 10.

                                      TABLE 9                                      __________________________________________________________________________     Catalyst                   Solvent     Reaction                                            Amount                                                                              EPU.sup.(1)                                                                         HCHO.sup.(2)                                                                               Amount                                                                              Time                                    Example                                                                             Type   (mmoles)                                                                            (mmoles)                                                                            (mmoles)                                                                            Type   (g)  (hrs)                                   __________________________________________________________________________     45   H.sub.4 Mo.sub.12 PO.sub.40                                                           0.10 101.37                                                                              10.72.sup.(3)                                                                       CH.sub.3 COOH                                                                         30   4.0                                     46   "      "    203.59                                                                              10.76.sup.(3)                                                                       "      "    "                                       47   "      "    50.97                                                                               10.77.sup.(3)                                                                       CH.sub.3 NO.sub.2                                                                     "    "                                       48   H.sub.4 W.sub.12 PO.sub.40                                                            "    51.34                                                                               10.86.sup.(3)                                                                       "      "    "                                       49   "      "    50.60                                                                               10.12.sup.(4)                                                                       CH.sub.3 CN                                                                           "    2.0                                     50   "      "    53.38                                                                               11.29.sup.(3)                                                                       ClCH.sub.2 CH.sub.2 Cl                                                                "    "                                       51   "      "    49.63                                                                               10.49.sup.(3)                                                                       Sulfolane.sup.(10)                                                                    "    "                                       52   "      "    50.95                                                                               10.77.sup.(3)                                                                       o-dichloro-                                                                           "    "                                                                  benzene                                             53   "      "    51.03                                                                               10.79.sup.(3)                                                                       cyanobenzene                                                                          "    "                                       54   "      "    49.99                                                                               10.57.sup.(3)                                                                       dinitrotoluene                                                                        "    "                                       55   "      "    50.76                                                                               10.73.sup.(3)                                                                       p-nitrotoluene                                                                        "    "                                       56   "      "    50.04                                                                               10.01.sup.(4)                                                                       nitrobenzene                                                                          "    "                                       57   "      "    100.67                                                                              10.65.sup.(3)                                                                       "      "    "                                       58   "      "    204.57                                                                              10.81.sup.(3)                                                                       "      "    "                                       59   "      "    51.02                                                                               10.20.sup.(5)                                                                       "      "    "                                       60   H.sub.4 W.sub.12 PO.sub.40                                                            0.10 51.14                                                                               10.29.sup.(6)                                                                       nitrobenzene                                                                          30   2.0                                     61   H.sub.4 W.sub.12 SiO.sub.40                                                           "    51.46                                                                               10.88.sup.(3)                                                                       "      "    "                                       62   HPK-40.sup.(7)                                                                        5 ml 50.60                                                                               10.12.sup.(5)                                                                       CH.sub.3 COOH                                                                         "    4.0                                     63   PK-228.sup.(8)                                                                        "    51.31                                                                               10.85.sup.(3)                                                                       "      "    "                                       64   KSF/O.sup.(9)                                                                           2.02 g                                                                            50.17                                                                               10.03.sup.(4)                                                                       nitrobenzene                                                                          "    2.0                                     65   H.sub.4 W.sub.12 PO.sub.40                                                            0.10 101.20                                                                               5.35.sup.(3)                                                                       "      60   "                                       __________________________________________________________________________      Note:                                                                          .sup.(1) Ethylcarbanilate                                                      .sup.(2) Converted to a formaldehyde basis.                                    .sup.(3) A 37% by weight aqueous solution of formaldehyde.                     .sup.(4) Trioxane                                                              .sup.(5) CH.sub.2 (OCOCH.sub.3).sub.2                                          .sup. (6) CH.sub.2 (OC.sub.2 H.sub.5).sub.2                                    .sup.(7) Cation exchanger containing sulfonic acid groups: trade name          Diaion HPK40, produced by Mitsubishi Chemical Industries Ltd.                  .sup.(8) Cation exchanger containing sulfonic acid groups: trade name          Diaion PK228, produced by Mitsubishi Chemical Industries Ltd.                  .sup.(9) Montmorillonite KSF/O, produced by Gardler Chemical Co.               .sup.(10) Tetrahydrothiophene1,1-dioxide                                 

                  TABLE 10                                                         ______________________________________                                         Conversion of.sup.(1)                                                                          Yield.sup.(2)                                                  EPC             (%)                                                            Example (%)         Dimer.sup.(3)                                                                            MDU    4,4'-MDU                                  ______________________________________                                         45      19.0        92.4      78.1   67.7                                      46       9.1        97.8      79.1   68.2                                      47      37.5        76.8      66.3   59.4                                      48      37.5        80.6      71.9   64.3                                      49      32.6        65.2      53.3   48.6                                      50      39.2        74.2      57.2   48.6                                      51      38.5        68.4      46.0   40.1                                      52      37.9        72.9      60.5   50.6                                      53      34.7        65.5      34.7   30.7                                      54      42.4        85.4      77.3   67.9                                      55      40.9        79.5      71.6   62.5                                      56      39.7        79.6      73.5   64.0                                      57      24.0        93.0      82.4   72.0                                      58      11.7        98.1      83.9   72.7                                      59      24.9        57.1      54.0   46.3                                      60      37.3        74.9      67.8   59.2                                      61      41.1        78.0      65.7   56.7                                      62      28.4        58.6      51.7   43.8                                      63      29.1        63.3      24.0   20.3                                      64      41.1        73.1      63.6   57.3                                      65       5.5        98.7      89.0   78.3                                      ______________________________________                                          Note:                                                                          .sup.(1) Conversion of ethylcarbanilate                                        ##STR11##                                                                      .sup.(2) Same as defined in Table 6.                                           .sup.(3) Same as defined in Table 6.                                      

What is claimed is:
 1. A process for producing a methylenedicarbanilate which comprises reacting a carbanilate with formaldehyde compound in the presence of at least one catalyst selected from the group consisting of:(1) heteropolymolybdic acid; and (2) heteropolytungstic acid.
 2. A process as in claim 1 wherein the carbanilate is represented by the formula ##STR12## wherein R is an alkyl group containing from 1 to 4 carbon atoms or a phenyl group, and X, Y and Z are each hydrogen, a halogen atom, a nitro group, an alkyl group containing from 1 to 5 carbon atoms, an alkoxy group containing from 1 to 5 carbon atoms, or an alkoxy carbamoylphenylmethyl group wherein the alkoxy portion contains from 1 to 4 carbon atoms.
 3. A process as in claim 1 wherein the carbanilate is a member selected from the group consisting of methylcarbanilate, ethylcarbanilate, phenylcarbanilate, 2,4'-methylenebis(ethylcarbanilate) and 4,4'-methylenebis(ethylcarbanilate).
 4. A process as in claim 1 wherein the formaldehyde compound is at least one member selected from the group consisting of gaseous formaldehyde, an aqueous solution of formaldehyde, trioxane, paraformaldehyde, acetals of formaldehyde, acylals of formaldehyde and oxymethylenebiscarboxylates.
 5. A process as in claim 1 wherein the carbanilate is used in an amount of at least 2 moles per mole of formaldehyde compounds, converted to a formaldehyde basis.
 6. A process as in claim 1 wherein the carbanilate is used in an amount of from 3 to 10 moles per mole of formaldehyde compounds, converted to a formaldehyde basis.
 7. A process as in claim 1 wherein the process is carried out by suspending the catalyst in a liquid phase or carried out in a uniform liquid phase and the acid catalyst is used in an amount of from 0.1 to 500 mmoles per mole of the carbanilate.
 8. A process as in claim 7 wherein the acid catalyst is used in an amount of from 1 to 100 moles per mole of the carbanilate.
 9. A process as in claim 1 wherein the process is carried out using a fixed bed catalyst and wherein the carbanilate is supplied to the reaction at a rate of from about 0.1 to 100 moles/hr per liter of the catalyst.
 10. A process as in claim 1 wherein the reaction is carried out in the presence of a solvent.
 11. A process as in claim 10 wherein at least one component of the solvent is a member selected from the group consisting of aliphatic carboxylic acids, nitroalkanes, aromatic nitro compounds, halogenated alkanes, aromatic halides, nitriles, and cyclic sulfones.
 12. A process as in claim 1, wherein said heteropolymolybdic acid is H₃ Mo₁₂ PO₄₀, H₄ Mo₁₂ TiO₄₀, H₈ Mo₁₂ CeO₄₂, H₈ Mo₁₁ GeO₃₉, H₆ Mo₉ MnO₃₂, H₅ Mo₆ IO₂₄, H₉ Mo₆ CrO₂₄, H₆ Mo₁₈ As₂ O₆₂, H₅ Mo₁₀ V₂ PO₄₀, H₆ W₉ V₃ PO₄₀, or HCs₃ Mo₁₂ SiO₄₀.
 13. A process as in claim 1, wherein said heteropolytungstic acid is H₃ W₁₂ PO₄₀, H₄ W₁₂ SiO₄₀, H₃ W₁₂ VO₄₀, H₆ W₆ TeO₂₄, H₆ W₁₈ P₂ O₆₂, H₆ W₉ V₃ PO₄₀, or HCuW₁₂ PO₄₀. 